Volume 13 Issue 1

This paper presents a kinetic study of ethanol production by simultaneous saccharification and fermentation (SSF) from Mn(II)-catalyzed cornstalks. The optimal conditions of ethanol production were as follows: 1:2 inoculation proportion (ratio of Pachysolen tannophilus to Saccharomyces cerevisiae), 30 °C fermentation temperature, 15% inoculation quantity, 4 mg/g addition amount of Mn2+, and 10 U/g cellulase dosage. An optimal ethanol yield of 0.359 g/g was obtained from cornstalks under optimum conditions. A 38.5% increase in the yield was observed compared with the control group without the addition of Mn2+. The relationship between ethanol yield and fermentation time followed a Langmuir isotherm model. The relationship between the rate constant and fermentation time in the conversion of cornstalks to ethanol was fractal like. The findings elucidate the complex characteristics of ethanol production from cornstalks with Mn2+ catalysis and will be useful in improving production yield.

The yield of macadamia shells (MSs) is huge. The preparation of hydrochar of MSs for the purpose of energy has broad prospects. This study investigated the possible optimum conditions for the most appropriate yield and higher heating value (HHV) of hydrochar through hydrothermal carbonisation (HTC) of MSs. The yield and HHV via HTC were systematically analysed by response surface methodology (RSM) using a synthetic weighted scoring method. The operating parameters included reaction temperature, reaction time, and water-to-biomass ratio. According to the mathematical model of RSM, the maximum response value was obtained under the following optimum conditions: reaction temperature, 220 °C; reaction time, 60 min; and water-to-biomass ratio, 11. The results showed that the reaction temperature exerted more remarkable influence than time and water-to-biomass ratio. Under the optimal conditions, the hydrochar yield and HHV were 57.58% and 22.69 MJ/kg, respectively. The results of elemental, proximate, Brunauer–Emmett–Teller, scanning electron microscopy, and Fourier transform infrared spectroscopy analyses showed that the hydrochar fuel properties improved compared with those of raw MSs. Furthermore, the surface structure and functional groups changed.

Lipase and cutinase belong to the esterase family and have biological applications in many fields. To develop more efficient biocatalysts that can be used for waste paper deinking, a chimeric lipase-cutinase (Lip-Cut) was constructed and successfully overexpressed in Pichia pastoris. The chimeric Lip-Cut exhibited lipase and cutinase activities that were 127% and 210% higher than their parent enzymes, respectively. Cut was superior to Lip in ink removal and improvement of paper brightness than Lip. The Lip-Cut displayed a better ink removal efficiency and paper brightness than that of the Lip, Cut, and Lip/Cut mixture. When the chimeric Lip-Cut was used, the ink removal efficiencies were 25.8% and 16.2% higher than that of the control-treated laser-printed paper and newspaper, which had sheet brightness values of 88% ISO and 59% ISO, respectively. The results demonstrated that the proper construction of bi-functional Lip-Cut could enhance the catalytic properties through the synergistic action of the two moieties because of the complementary advantages in the substrate specificities and catalysis patterns of both enzymes. This may provide an effective way to engineer more efficient bi-functional lipases and cutinases for deinking waste paper.

The effects of temperature, reaction time, biomass/water feedstock ratio, NaOH concentration, and ZSM-5 catalyst amount were investigated relative to the hydrothermal liquefaction (HTL) of sugarcane bagasse. The experimental results showed that the maximum yield of bio-oil (46.9%) was achieved with the following conditions: 10 g of sugarcane bagasse, 200 mL of distilled water, 30 min, and 285 °C. It was seen that the products of oxygenation (phenols, acids, ketones, alkenes, and esters) were abundant in the bio-oil. With the addition of NaOH, the residue yield decreased remarkably, and the yield of organics dissolved increased. The yields of acids and furfurals in the bio-oil decreased with the presence of NaOH during HTL. Additionally, ZSM-5 effectively decreased the acidic compounds and improved the liquid properties during HTL. Sugarcane bagasse in HTL with catalysts significantly improved the quality of bio-oil with lower oxygen content and higher HHV. Moreover, the gaseous products H2 and CH4 were noticeably affected by the temperature, NaOH concentration, and ZSM-5 amount.

Hydrothermal carbonization (HTC) is an efficient conversion process that treats solid digestates from anaerobic digestion plants and converts it into valuable solid products. In this study, digestates of swine manure (DS_M) and rice straw (DS_S) were HTC-treated at 190 °C with biomass-to-water ratios of 1:4 and 1:9. The hydrochars were characterized physically and chemically to elucidate their potential as a valuable resource. The hydrochars from the solid digestates were acidic, and the dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and Brunauer-Emmett-Teller surface area (SBET) were significantly (P < 0.05) higher compared with that of the feedstocks and pyrochars. Mesopores were dominant in the hydrochars, where the pores had slit-type holes and a stratified structure. The hydrochars possessed more O functional groups and aromatic C=C and C-H band than the feedstocks and pyrochars. The hydrochars derived from solid digestates were better as a solid fuel because of their combustion property. The increase in the crystallinity of the hydrochars enhanced their stability. The hydrochars produced from the DS_M were more acidic than those from the DS_S. The HTCDS_S had a better adsorptive effect on pollutants than the HTCDS_M because of the higher SBET and optimal functional groups.

The appropriate diameter ratio of log top and butt ends when using a round bar (cylinder shape) as a log model for estimating the density and Young’s modulus of a log was investigated. Square timbers of Japanese cedar (Cryptomeria japonica D. Don) with a length of 1200 mm were used as specimens and were machined into circular truncated cones. A longitudinal vibration test was performed to obtain the Young’s moduli of the square timbers and the circular truncated cones. The Young’s moduli were calculated using the circular truncated cone model and the round bar model. The density and Young’s modulus calculated by the circular truncated cone model were similar to those of the square timbers. Hence, it is considered that the circular truncated cone was effective for estimating the densities and Young’s moduli of logs. The density and Young’s modulus calculated by the round bar model differed from those of the square timbers when the diameters of the top ends were small. However, it is considered that the round bar can be used as a log model for actual logs.

Several potential approaches were evaluated to improve the physical and mechanical properties of 3 mm HDF panels used as door-skins. Six different composition recipes were applied by varying the ratio of hardwood-to-softwood fibers and the addition of bark. The density, surface absorption, bending strength, modulus of elasticity, and internal bond of the HDF panels manufactured on an industrial line were determined. The best performance was obtained for the recipe with 20% hardwood fibers, 80% softwood fibers, and less than 5% bark. The influence of spraying the fiber mattress before pressing, by means of water and two different release agents, was also tested. The obtained results are applicable at any HDF producer and can be used for process optimization.

Cellulose nanofibrils (CNFs) were oxidized by the TEMPO oxidation system from bleached kraft eucalyptus pulp, and layered double hydroxides (LDHs) were prepared via the hydrothermal method. MgAl-CO₃-LDHs/CNFs composite films with different LDH ratios were prepared via a filtering/evaporation technique that endowed the nanocomposites with barrier and strengthening properties. The MgAl-CO₃-LDHs could uniformly disperse in the CNFs matrix with an improved reciprocal adhesion, and the surface result was smooth and continuous. The basic structure of the membrane did not change, but the thermodynamic properties and the water vapor barrier property improved. This composite membrane can be widely used in food, pharmaceutical, and chemical packaging industries as a gas-liquid barrier material.

Chlorine dioxide bleaching is an important component of elemental chlorine-free bleaching. A method is introduced in this work to optimize process conditions for chlorine dioxide delignification based on nonlinear programming and response surface analysis. An energy consumption model for chlorine dioxide bleaching is established, as well as statistical models for the brightness, viscosity, and absorbable organic halogen content with the process conditions. The results from the model predict that the cost can be reduced compared to the optimization results of the response surface analysis and experiments.

Tungsten trioxide (WO₃), which is a semiconductor, was hydrothermally synthesized onto the surface of wood. After the in-situ synthesis of WO₃ nanoparticles on the wood surface, the wood exhibited photochromic and superhydrophobic properties. The WO₃ nanostructures were fabricated on wood surface through a two-step hydrothermal process at 90 °C or 120 °C for 6 h. Chemical composition, crystalline structures, and morphologies of the WO₃-coated wood were characterized. The results indicated that the amount of WO₃ nanostructures on the surface of the wood substrate was 12.89 wt.%. Meanwhile, the WO₃ nanostructures were composed of fine nanoparticles and highly crystallized by SEM and XRD analysis. When the sample was irradiated under ultraviolet (UV) light (365 nm), there was an obvious color change after 10 min (ΔE). The water contact angle measurements demonstrated that the fluorosilane modified WO₃-coated wood surfaces possessed a superhydrophobic behavior with a contact angle of 152°. The sliding angle was less than 10°. Photochromic and superhydrophobic properties were achieved by a facile process, which could contribute to the development of functional wood with an aesthetic coloring.